Wet cleaning apparatus and methods

ABSTRACT

Apparatus for wet cleaning is disclosed. In one example, such an apparatus includes first and second Sulfuric Acid Peroxide Mixture (SPM) baths for removing photoresist on semiconductor wafers that are sequentially provided; a Hot Quick Dump Rinse (HQDR) bath for cleaning the wafers conveyed from the first and second baths; first and second Ammonium Peroxide Replacement (APR) baths for cleaning particles and organic residues remaining on the wafers conveyed from the HQDR bath; and a drier for drying the wafers conveyed from the first and second APR bath.

TECHNICAL FIELD

The present disclosure relates to semiconductor fabrication technologyand, more particularly, to wet cleaning apparatus and methods.

BACKGROUND

Generally, semiconductor integrated circuit (IC) chips are fabricated bysubjecting a silicon wafer to sequential and repeated processes ofphoto, etch, ashing, ion diffusion, and thin-film deposition processes.

In this wafer fabrication process, the photo process includes: adeposition step of photoresist having optical sensitivity on the surfaceof the wafer; a step for placing a reticle having circuit patterns to bemanufactured in the wafer; an exposure step for transferring the circuitpatterns of the reticle to the deposited photoresist by irradiating thewafer with light having a predetermined wavelength; and a developmentstep for developing the exposed photoresist to form the circuit patternsin the wafer.

In the photo process, some portions of layers underlying the photoresistare etched and removed using the photoresist pattern that remains afterthe development process, and then remaining photoresist pattern isremoved by an ashing step.

The ashing step can be divided into two steps: a wet ashing step inwhich chemicals are used in the removal of the patterned photoresist;and a dry ashing set in which a predetermined ashing gas such as plasmaand ozone is used to expunge the patterned photoresist.

FIG. 1 shows known wet cleaning equipment such as post-ashing equipmentperforming the wet ashing process and post-treatment equipmentperforming SH cleaning after the Chemical Mechanical Polishing (CMP).

Referring to FIG. 1, the conventional wet cleaning equipment comprises aSulfuric Acid Peroxide Mixture (SPM) bath 102, a Chuck/Clean (C/C) 104,a Hot Quick Dump Rinse (HQDR) bath 106, an Ammonium Peroxide Replacement(APR) bath 108, and drier 110. In the conventional equipment, the SPMbath 102 contains mixture of H₂SO₄ and H₂O₂ (SPM), the C/C 104 is forcleaning a robot chuck that carries wafers, and the APR bath 108 is toclean particles and organic residues remaining on the wafer.

Further, the APR bath 108 is structured as a single bath type by whichtwo processes for chemical treatment and rinse are conductedsimultaneously. In order to perform the necessary processes with the APRbath 108, it a tank 108′ is needed to mix an alkali chemical, H₂O₂ andhot Deionized Water (DIW). The mixture 112 is heated to 70° C., and isthen provided from the tank 108′ to the APR bath 108.

With the conventional equipment having the structure explained above,the conventional wet cleaning process is performed in the order of SPMcleaning step→HQDR cleaning step→APR cleaning step→dry step. Thisprocess normally takes about 38 minutes in these steps per singlearrangement of equipment. That is, the throughput time of theconventional wet cleaning process per equipment is about 38 minutes.

For reducing the processing time and improving the throughput,investment in additional equipment is necessary. However, such purchasesincrease fabrication cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of conventional wet cleaning equipment.

FIG. 2 is a schematic diagram of example disclosed wet cleaningequipment.

DETAILED DESCRIPTION

Disclosed herein are a wet cleaning apparatus and cleaning methodsadapted to be used in post-ashing equipment that is employed in removingphotoresist.

As shown in FIG. 2, an APR bath which has significant effect on thethroughput time is provided additionally, a capacity of a tank forproviding mixed solution to the APR bath is increased, and an SPM bathis added, so that the overall throughput time is cut in half whencompared with the throughput time of the conventional equipment.

Referring to FIG. 2, one example of disclosed wet cleaning equipmentincludes first and second SPM bath 12 a and 12 b, a C/C 14, a HQDR bath16, first and second APR baths 18 a and 18 b, a tank 18′, and a drier20. The tank 18′ mixes alkali chemical, H₂O₂ and DIW. Further, the tank18′ heats the mixed solution 22 to a processing temperature, andprovides the heated mixed solution to the first and second APR baths 18a and 18 b.

The tank 18′ has an increased capacity to accommodate the addition ofthe APR bath by making, for example, the capacity of the deionized waterto be 24 liters and the power of the heater to be 24 kilowatts (KW), ascompared with the conventional tank (108′ of FIG. 1) of 18 liters ofdeionized water capacity and 12 KW power of heater. With this structureof the tank 18′, time in preparing for the mixed solution to be providedto the first and second baths 18 a and 18 b is cut in half in comparisonwith the conventional equipment. For instance, the time for thepreparation is reduced to about less than 15 minutes by disclosedexample.

Now, the method for cleaning by using the wet cleaning equipment isexplained.

A wafer cassette (hereinafter ‘first wafer cassette’) having a number ofwafers that have patterned circuits formed by the photo process isloaded and conveyed by a loader to the first SPM bath 12 a where H₂SO₄and H₂O₂ is mixed by a predetermined weight ratio (for example, 6:1) tobe subjected to the photoresist removal process.

During the process for removing the photoresist is performed, anotherwafer cassette (hereinafter ‘second wafer cassette’) is loaded to thesecond SPM bath 12 b, and the photoresist patterned on the second wafersare removed.

The loading of the first and second wafer cassette to the first andsecond SPM baths 12 a and 12 b is conducted with a predetermined timedifference.

The first wafer cassette, after the removal of photoresist at the firstSPM bath 12 a, is transferred to the HQDR bath 16 for the wafer cleaningprocess, and then conveyed to the first APR bath 18 a that containsalkali chemical (e.g., ammonia (NH₄OH)), H₂O₂, and DI water of apredetermined weight ratio of, for example 0.2:1:10 to be subjected tocleaning particles and organic residues and drying in the drier 20.

When the first wafer cassette is conveyed to the first APR bath 12 a,the second wafer cassette is moved to the HQDR bath 16 for cleaning. Thesubsequent processing of the second wafer cassette is the same asconducted for the first wafer cassette.

By using the disclosed processing, the time consumed by cleaning wafersof a wafer cassette is reduced to less than 20 minutes, which amounts toabout a half of the conventional time.

Disclosed herein are methods and apparatus for wet cleaning that canreduce the throughput time and prevent increased equipment investment.

According to one particular example, wet cleaning equipment may includefirst and second Sulfuric Acid Peroxide Mixture (SPM) baths for removingphotoresist on semiconductor wafers that are sequentially provided; aHot Quick Dump Rinse (HQDR) bath for cleaning the wafers conveyed fromthe first and second baths; first and second Ammonium PeroxideReplacement (APR) baths for cleaning particles and organic residuesremaining on the wafers conveyed from the HQDR bath; and a drier fordrying the wafers conveyed from the first and second APR bath. In oneexample, the first and second baths include a tank that heats a mixedsolution of alkali chemicals, H₂O₂, and deionized water to a processingtemperature and provides the heated mixed solution to the first andsecond APR baths.

One example disclosed method includes using first and second SPM baths,a HQDR bath, and first and second baths. The first plurality of wafersin a first wafer cassette are cleaned by passing through the first SPMbath, the HQDR bath and the first APR bath, while second plurality ofwafers in a second wafer cassette are cleaned by passing through thesecond SPM bath, the HQDR bath and the second APR bath.

Although certain apparatus constructed in accordance with the teachingsof the invention have been described herein, the scope of coverage ofthis patent is not limited thereto. On the contrary, this patent coversevery apparatus, method and article of manufacture fairly falling withinthe scope of the appended claims either literally or under the doctrineof equivalents.

1. An apparatus for performing removal of photoresist and SH cleaning,comprising: first and second Sulfuric Acid Peroxide Mixture (SPM) bathsto remove photoresist on semiconductor wafers that are sequentiallyprovided; a Hot Quick Dump Rinse (HQDR) bath to clean the wafersconveyed from the first and second SPM baths; first and second AmmoniumPeroxide Replacement (APR) baths to clean particles and organic residuesremaining on the wafers conveyed from the HQDR bath; and a drier to drythe wafers conveyed from the first and second APR baths.
 2. An apparatusas defined by claim 1, further including a tank that heats a mixedsolution of alkali chemicals, H₂O₂ and deionized water to a processingtemperature and provides the heated mixed solution to the first andsecond APR baths.
 3. A method for wet cleaning by using first and secondSPM baths and a HQDR bath, wherein first plurality of wafers in a firstwafer cassette are cleaned by passing through the first SPM bath, theHQDR bath and the first APR bath, while second plurality of wafers in asecond wafer cassette are cleaned by passing through the second SPMbath, the HQDR bath and the second APR bath.